题干
— Are there any flowers _______ the tree.
— No. But there are many birds _________ it.
A：in, on
B：in, in
C：on, in
D：on, on
答案(点此获取答案解析）
C
— Are there any flowers _______ the tree.
— No. But there are many birds _________ it.
A：in, on
B：in, in
C：on, in
D：on, on
，（t>0）是角
终边上的一点，则当
最小时，
（ ）